Diagnosing dementia:

Any appropriately skilled clinician can make the diagnosis and brain scanning not always needed

Dementia is a clinical syndrome and at one level simply implies brain failure (analogous to heart failure or liver failure). The diagnosis is a two stage process.

First, to make a diagnosis of dementia you need to differentiate it from: depression; delirium; the effect of drugs and; the changes in memory expected as part of normal ageing. Two key features for a diagnosis of dementia are that the patient’s symptoms should affect daily living activities and be progressive. Second is to determine the cause of condition – the commoner causes are Alzheimer’s disease, vascular dementia and Lewy body dementia.

Both stages are based on a comprehensive assessment including a history, including one from someone who knows the patient well, a physical and mental state examination, including a specific assessment of cognitive function, a functional assessment and selected ancillary investigations (Dementia: NICE Clinical Guideline 42, www.NICE.org).

Any clinician who has the appropriate skills can recognise and make a diagnosis of dementia, once it is established. Specialist advice is more likely to be needed in the early stages and in particular clinical situations such as when the presentation or course is atypical, where significant risks are identified where the picture is complicated by behavioural or psychological symptoms and in groups such as people with learning disabilities.

Specialist advice may also be needed to establish the exact cause of the dementia. This may have clinical implications for the prescription of medication such as drugs for Alzheimer’s disease, treatment of vascular risk factors in vascular dementia or avoidance of antipsychotics in Lewy body dementia.

In terms of brain scanning, the NICE Dementia Guideline states “Imaging may not always be needed in those presenting with moderate to severe dementia, if the diagnosis is already clear.” This may particularly apply to older and frailer patients with established dementia.

Post diagnostic support which should be person centred goes hand in hand with the diagnosis (which does not necessarily have to result in the prescription of medication) and is largely independent of the cause of the dementia.